The U.S. International Trade Commission (USITC) has terminated its investigation against Philadelphia Solar USA and Trina Solar after First Solar withdrew its complaint alleging infringement of its U.S. patent claims related to TOPCon solar cells, modules, and related products.

The Commission decided not to review an administrative law judge’s initial determination granting First Solar’s request to withdraw its complaint against Philadelphia Solar and Trina Solar.

First Solar filed its motion to terminate the investigation against Philadelphia Solar USA and Trina Solar on June 8, 2026. The Office of Unfair Import Investigations supported the motion in a filing dated June 18, 2026.

USITC had initiated the Section 337 investigation into imports of TOPCon solar cells and modules this March based on First Solar’s complaint.

The complaint alleged violations of Section 337 of the Tariff Act, 1930 related to the importation and sale of certain TOPCon solar cells, modules, panels, components, and products containing them.

The investigation originally named multiple respondents, including manufacturers and subsidiaries associated with Canadian Solar, JA Solar, JinkoSolar, Trina Solar, Runergy, Hanwha Q CELLS, Adani Group companies, Toyo, and VSUN.

The respondents were based across the U.S., China, India, Vietnam, Thailand, Malaysia, Germany, Canada, Hong Kong, Jordan, Japan, and South Korea. The Office of Unfair Import Investigations was also named a party to the investigation.

BYD America and Tesla were added to the investigation through intervention during the proceedings. The USITC notice stated that Mundra Solar Energy and Adani Green Energy were previously terminated from the investigation after First Solar withdrew its complaint against those respondents.

Earlier in March, the Office of the United States Trade Representative initiated a Section 301 investigation into structural excess capacity and manufacturing production, with India among the economies under review. The investigation will examine whether policies or practices in these economies contribute to structural overcapacity in manufacturing sectors, which could distort global markets and harm U.S. commerce.